Water droplets of spray or "tread throw", hereinafter referred to as "throw" are thrown from rotating tires of vehicles traveling on wet road surfaces and impact against surfaces of the vehicle, causing the spray droplets to fragment into smaller droplets of mist. This presents the problem of impaired visibility to the drivers of these and other vehicles during wet conditions. Water thrown from the tires generally comprises large and small water droplets, some in the form of a mist or even a fog. Tests have demonstrated erratic directional control by drivers of following cars and trucks which are enveloped in this mist, especially that from large commercial trucks and tractor-trailer combinations which are moving ahead of them or beside them as they travel on the wet roadways. Drivers of these large vehicles also have difficulty seeing, via their rear view mirrors, through the spray generated by their own vehicles which occasionally causes accidents as these vehicles change lanes.
Several devices and apparatus for controlling road spray have been developed to reduce the impaired visibility for these drivers. For example, F. D. Roberts, in his U.S. Pat. No. 3,341,222 discloses a Vehicle Wheel Spray Collector which has alternate upward and downward flaring channels with slots spaced apart and located at the top of the upward flaring channels. These channels when arranged in the shape of a fender, collect water from the spray in the bottom of the downward flaring channels, which is thrown from the tires through the slots at the top of the upward flaring channels. A trough at the bottom of the collector collects the water and deposits it outside the tracks of the tires of the vehicle. The function of Roberts' invention is to collect the throw droplets rather than to directly coalesce, directly suppress, or direct the throw. Roberts' spacing and size of the slots in the channels and the excessive height of his corrugations, which are considered to be his wedges, permit spray to fall back onto the rotating tire beneath the collector to spray again.
Brandon et al. in their U.S. Pat. No. 4,258,929 disclose a Vehicle Spray Reduction Apparatus utilizing an unperforated mud flap having V's facing the throw above and behind tires and troughs behind the V's to carry the water rearward above the tires and to protect the downward flow behind the tires.
Reddaway in his U.S. Pat. No. 3,899,192 presents a Fender Flap Spray Controller which uses an artificial turf surface to collect the spray, wherein the water flows down behind the surface matting of the fender flap and is channeled away from the tires.
Roberts et al. in their U.S. Pat. No. 4,205,861 disclose an Automotive Vehicle Wheel Spray Collector, utilizing Roberts' earlier flaring channel design of his U.S. Pat. No. 3,341,222 in which flanges beside the slots and a ridge in the formerly flat backing is now used behind the channels and slots to deflect the spray droplets into the bottom of the downward flaring channels, within the water collecting tank beyond the channels. His wedges are too high and therefore some water flowing along them at an angle slows down, stops and falls back upon the tires to create more spray rather than entering the slots.
Irving in British Patent No. 1,584,453 discloses Improvements in Mud Flaps similar to Roberts' flaring fender, in which one or two layers of open-ended channel members guide spray into a containment region, in which it coalesces to form water which runs down in vertical V's and is deposited on the pavement near the center of the trailer.
Other fender flap designs such as the rubber button flaps made by National Rubber Company, also made by Buxbaum Company and also made by Konetta Company, are designed to suppress formation of mist from the high speed throw from tires. The Konetta spray control system is the system described by Lightle, et al. in their patent 4,382,606 of 1983. Lightle describes the function of these ribs and of those on the "splash guard" behind the wheel as "flow control" to direct the condensed water to flow in the desired direction. They have little to do with condensation and coalescence which are accomplished by the vertical wall of the skirt and the buttons or cones on the splash guard. The ten degree slope of the ribs simply eases removal from the mold. The ribs were neither intended to nor are they capable of suppressing speed throw. They use side skirts with vertical ridges separated longitudinally by 1 1/2 inches to coalesce the water and to direct it to drain vertically downwardly thus preventing the rearward flow valued by side skirts of this invention which have horizontal wedges or ridges the distance between upper surfaces being between 1/2 and 2 inches.
In Heinz-Henning Jurges' U.S. Pat. No. 4,427,208 of 1984, his mudguard is used to prevent spray generated over, behind and ahead of the wheel from travelling laterally. Rather, it lets the water fall back upon the tire to spray again. Jurges' ribs or wedges are widely spaced apart and decrease in height as they approach the outer edge, continuing down the splash protector edge outside the wheel. These ribs or wedges will not carry water to fall near a splash guard because they are too small in profile and have a 50 degree symmetric vertex angle. In addition the downward slope of the fender and the air motion forward of the wheel blow the water back onto the tire in a crosswind and prevent these ribs from functioning as do the horizontal ribs and wedges of this invention.
Maurice Goodall, in his U.S. Pat. No. 4,290,609 of 1981 discloses gutters to carry collected water. His design does not include wedges, but provides screens for spray control. His screens are complex and difficult to clean, contrasting with the open ridges and wedges of this invention. He uses ram air rather than normal air flow to force the water rearward. His screens will quickly fill with dirt and ice and are not selfcleaning.
Pete A. Schons in his U.S. Pat. No. 3,834,732 of 1974 discloses a spray collector like Roberts' spray collector. Removing Schons' openings would prevent spray control.
Thaddeus M. Ochs in his U.S. Pat. No. 3,473,825 of 1979 shows and describes stiffeners that run down both edges of the flap to prevent lifting and twisting, thereby holding this fender flap in position in the presence of the high speed air flow.
Harold V. Conner in his U.S. Pat. No. 3,877,722 of Apr. 15, 1975 describes a vertical stiffener attached to the fender flap and to rigid cross members at top and bottom to reduce twist and lift.
Ross A. McKenzie and Hans Busch in their U.S. Pat. No. 4,398,734 of 1983, include an overwheel splash guard with a solid base and rubber nipples facing downward, which permit the coalesced overwheel water to fall on the tire to make more spray. Also they provide a fender flap spray controller with rows of rubber buttons facing the spray. These rubber buttons suppress the spray and collect water that flows between the rows of rubber buttons, to ultimately fall to the surface below.
James E. Clutter in his U.S. Pat. No. 4,436,319 of 1984 uses a tank shaped like a fender having inner and outer walls separated by about one inch, similar to Roberts' fender, except that he uses laterally extending flanges around the periphery and flanges extending in the direction of rotation in the side portions to guide the throw into the tank. The water flow is not along the flanges, but transverse to them, the flanges deflecting the water into the tank from which it is drained to fall outside the paths of the tires. The flange openings and interior of the tank are not self-cleaning. The system ceases to function when filled with dirt and is very difficult to clean, except the exterior fender-like surfaces.
Fritz Buchner, in her German patent, reference DE 3635854 dated Oct. 22, 1986, shows an alternate method to trap the upward moving throw behind single axles. He has a forwardly and downwardly extending top portion of his fender flap which deflects the upwardly moving throw rearward to fall along the forward surface of the vertical part of his fender flap.
Although these specific prior advances have been made to try to control mist or spray, a significant improvement in visibility has not as yet been successfully accomplished by these earlier inventions as stated by the U.S. Department of Transportation in April 1988.
In reference to the history of these earlier inventions, the simple, flat fender flaps, also called mud guards, splash guards, or mud flaps, originally were hung behind rear tires to prevent mud from being thrown from roads onto following vehicles' windshields. Then fenders were used to improve the containment of mist, spray, and mud. However, with modern high speed travel on paved roadways, even widely separated ribs do not adequately suppress spray formation in fender flap or overwheel locations and narrow ribs alongside cannot carry the water to the fender flap location. Curved fender like wedge arrays with slots leading to containment regions are ineffective if the wedges are too high, thereby requiring condensed water from the throw, impacting at large angles from the radial direction, to flow too far along the wedge surface before entering the slots, flanged or otherwise, thereby allowing friction to stop it and it falls on the speeding tire to become copius spray.
It appears that earlier inventors did not achieve the savings and effectiveness of these simple flat arrays with low wedges for several reasons, such as their lack of awareness of:
the importance of keeping the angle of impact for overwheel slotted arrays near normal to the array;
the importance of using wedges having heights small enough to utilize the slots effectively, but large enough to effectively suppress mist formation;
the importance in reference to slotted arrays with straight slots, that is, slots perpendicular to the base, that the slots be deep enough in the direction of motion of the throw, i.e. base thickness, the wedge angle be large enough, the wedge height be high enough and the slot width in the lateral dimension be small enough, so that enough water accumulates in each straight slot to significantly reduce direct non-impact transmission of throw through the straight slots, this reduction thereby making it possible to eliminate the containment region and allowing the condensed water to flow directly to the road surface;
the importance or realization that following tires will have spray control equipment, and moreover, the largest amount of the water has been splashed laterally, so that the water returned to the tire tracks from the throw does not create a great problem;
the importance or realization that in using wedge arrays with slanted slots, the slots must be slanted enough and made long enough, i.e. the base made thick enough, to block direct transmission of spray;
the importance or realization that slanted slot arrays can be designed to deflect the condensed water in the direction desired, for example, over an overwheel array to fall inside the tires or with split flow, half inside and half outside the tires, a slight tilt downwardly toward the center assisting inward flow and a slight tilt downwardly and rearwardly of overwheel spray controllers behind single tires, duals and rear tandems assisting rearward flow of the deflected water;
the importance or realization that a crosswind blows the water from the bottom of a side skirt laterally to fall upon a tire and become spray again; and
the importance or realization that the air passing under a vehicle is in part dragged along with the vehicle and therefore that water made to fall inside the tire tracks into this dragged air between them, does not break into as fine a spray as that falling into the high shear airstream outside the tire tracks.